Clay minerals as a soil potassium reservoir: observation and quantification through X-ray diffraction |
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Authors: | Pierre Barré Christophe Montagnier Claire Chenu Luc Abbadie Bruce Velde |
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Affiliation: | (1) Laboratoire BioEMCO,UMR 7618, INRA-CNRS-UPMC-INAPG-ENS-ENSCP, Ecology department, Ecole Normale Supérieure, 46 rue d’Ulm, 75230 Paris cedex 05, France;(2) UMR 8538, Laboratoire de Géologie, ENS-CNRS, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France;(3) Centre de Versailles-Grignon, INRA, Unité expérimentale grandes cultures, route de Saint-Cyr, 78026 Versailles Cedex, France;(4) Laboratoire BioEMCO, UMR 7618, INRA-CNRS-UPMC-INAPG-ENS-ENSCP, INAPG, Batiment EGER, 78850 Thiverval Grignon, France |
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Abstract: | Potassium (K) is a major element for plant growth. The K+ ions fixed in soil 2:1 clay mineral interlayers contribute to plant K nutrition. Such clay minerals are most often the majority in temperate soils. Field and laboratory observations based on X-ray diffraction techniques suggest that 2:1 clay minerals behave as a K reservoir. The present work investigated this idea through data from a replicated long term fertilization experiment which allowed one to address the following questions: (1) Do fertilization treatments induce some modifications (as seen from X-ray diffraction measurements) on soil 2:1 clay mineralogy? (2) Are soil 2:1 clay mineral modifications related to soil K budget in the different plots? (3) Do fertilizer treatments modify clay Al, Si, Mg, Fe or K elemental content? (4) Are clay mineral modifications related to clay K content modifications? (5) Are clay mineral changes related to clay Al, Si, Mg or Fe content as well as those of K content? Our results showed that K fertilization treatments considered in the context of soil K budget are very significantly related to 2:1 soil clay mineralogy and clay K content. The 2:1 clay mineral modifications observed through X-ray measurements were quantitatively correlated with chemically analyzed clay K content. Clay K content modifications are independent from clay Al, Si, Mg or Fe contents. These results show that the soil chemical environment can modify interlayer site occupations (illite content) which suggests that high level accumulation of potassium can occur without any modification of the clay sheet structure. This study therefore validates the view of 2:1 clay minerals as a K reservoir easily quantifiable through X-ray observations. |
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Keywords: | Abiotic/biotic interactions Clay minerals Ecosystem functioning Long term experiment Potassium cycle Soil |
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